Recent Development and Perspectives of Solvents and Electrode Materials for Electrochemical Oxidative Degradation of Lignin

Lignin is the most abundant potential renewable resource of aromatic structural units. Turning lignin into high-value compounds, such as fuels, adhesives or refined chemicals, is the cornerstone and focus of biorefinery in the future. Depolymerization of lignin can convert its macromolecules towards smaller molecules (monomers or oligomers) allowing it to be used for further applications. Electrochemical depolymerization is an excellent method of green and sustainable transformation, which can effectively avoid reagent waste and mild reaction. This review pretents the research progress of lignin electrochemical oxidation in recent years, summarizes the effects of solvent system (alkaline solvent, ionic liquid and deep eutectic solvents, as well as different lignin concentration and medium), electrode materials (platinum, gold, copper, nickel, cobalt, lead dioxide, tin dioxide and titanium-based metal electrodes) and electrolytic parameters (current density, temperature, reaction time and photocatalysis) on the oxidative degradation efficiency and product distribution of lignin, and prospects its development. The development of low-cost electrode materials and efficient solvent systems will still be an important direction for the high-value and high-quality application of lignin.